LOOSE BALLIN’: Marshall Henderson of Mississippi has a sly, celebratory look during the second half of his team’s 57-46 victory over fifth-seeded Wisconsin yesterday. Photo: AP

KANSAS CITY, Mo. — Finally, Marshall Henderson had nothing to say.

Mississippi’s outspoken guard had been quieted throughout his long-awaited NCAA Tournament debut, hitting one of his first 13 shots. His mouth stopped moving. His swagger had slowed. His lifelong dream had become a non-stop nightmare.

“I was sitting on the bench and was like, ‘If I don’t pick this up, it’s going to be my fault. I don’t want it to be my fault,’ ” Henderson said. “I’ve shot like 20 hundred million shots in my day. Now that I make the NCAA Tournament, why does this happen?”

The self-proclaimed “Tasmanian Devil” kept running around screens, kept looking for the ball and kept doing what everyone knew he was going to keep doing — shoot.

With the season slipping away, the SEC’s leading-scorer finally found his touch, scoring 17 of his team’s final 27 points to help the 12th-seeded Rebels pull off a second-round upset over fifth-seeded Wisconsin, 57-46, yesterday in a West Region game at the Sprint Center.

“Listen, we’ve seen this show before,” Ole Miss coach Andy Kennedy said of Henderson’s second-half surge. “It doesn’t matter. Once he makes one or two, feed Henderson.”

After the brazen guard dropped a simple pass at half-court, which Wisconsin’s Sam Dekker converted into a basket to give the Badgers (23-12) a 36-30 lead with less than 12 minutes remaining, the spectacle everyone came to see broke free from the chains of Wisconsin’s stifling defense. Henderson hit back-to-back 3-pointers, tying the game at 36, and the beast was loose and ready to wreak havoc.

“We knew Henderson was going to get going,” said Wisconsin center Jared Berggren. “He got hot, did what he does.”

Henderson struck the most devastating blows with a running drive and a 3-pointer that put the Rebels up 50-44 with less than three minutes remaining, finishing with 19 points on 6-of-21 shooting. Not until the final seconds did Henderson start playing to the crowd — running around, wagging his tongue and swinging his arms in the air.

“You can’t go a little crazy when you went 1 for your first [13],” Henderson said. “I know when I can do it and when I can’t do it.”

Wisconsin, which had won six straight NCAA Tournament openers, did what it wanted, keeping the score low and the pace slow, while holding Ole Miss to a season-low scoring effort, but the Badgers matched Henderson’s early shooting struggles shot for shot.

Led by Dekker’s 14 points, Wisconsin shot 25.4 percent from the field and hit 7-of-30 3-pointers, yet still led 25-22 at halftime. In the second half, the Rebels dominated inside, getting big efforts from Reginald Buckner (12 points, nine rebounds, five blocks) and Murphy Holloway (10 points, nine rebounds), outscoring Wisconsin 30-16 in the paint.

“They just outworked us in the last eight or nine minutes, really took it to us and we didn’t know how to handle it,” Dekker said. “They just out-toughed us.”

And now, the Rebels are one game away from their first Sweet 16 in 12 years.

“We knew shots were going to fall and when they did, we knew we were going to win,” Henderson said. “I was just waiting for that first three to down. I told you all along, coach Kennedy has told me, I’ve got to be, what is it?”

Kennedy replied, “A serial killer.”

The first victim has been claimed. Beware. “Marshall Mania” is running wild.